This invention relates generally to downhole drilling in subterranean formations and, more particularly, to a hole opening tool and to methods of making the hole opening tool.
In the exploration of oil, gas and geothermal energy, drilling operations are used to create boreholes in the earth. One type of drilling operation includes rotary drilling. According to rotary drilling, the borehole is created by rotating a tubular drill string which has a drill bit coupled to one end. The drill bit engages a formation and produces a borehole of equivalent diameter to the drill bit as the drill bit proceeds downward. As the drill bit rotates and deepens the borehole, additional drill pipe sections are coupled to the end that does not have the drill bit so that the drill bit may further deepen the borehole. Typically, various components comprise the Bottom Hole Assembly (“BHA”). These may include, but are not limited to, measurement while drilling (“MWD”) tools, logging while drilling (“LWD”) tools, drill collars, downhole motors (“DHM”), and rotary steerable tools coupled to the drill string and located within the borehole above the drill bit.
During drilling operations, these BHA components are oftentimes subjected to constrictions in the wellbore brought on by various conditions. These constrictions may be found anywhere in the open hole wellbore. One such condition arises when the soil around the borehole swells thereby causing a constriction within the borehole. As the drill bit advances through the borehole, the soil above the drill bit may become exposed to moisture levels that may otherwise not prevail, thereby causing the soil to hydrate and swell. Another such condition arises when cuttings settle on the low side of the hole in high angle and lateral boreholes. These cuttings cause the borehole diameter to be constricted in the areas of the cutting settlings. Another such condition arises when sloughing occurs in some vertical or near vertical wellbores. In this situation, chunks of the borehole wall become dislodged above the BHA or around the BHA and fall to the top of the BHA or the drill bit. Thus, a blockage or constriction in the borehole is created. These conditions are but a few of the conditions that may cause constrictions within the wellbore.
These constrictions may cause difficulties during the drilling process, which includes retrieving the drill bit and other BHA components from the borehole. Since these components are very costly, it would be advantageous to be able to remove the BHA and drill bit while spending the least amount of downtime while doing so. Additionally, as constrictions form in the wellbore, problems may arise during the forward advancement of the drill bit through the borehole. Thus, a tool for opening these constrictions would facilitate the drilling process.
Prior systems have attempted to deal with some of these problems through the use of roller reamers and string reamers. Prior art reamers typically have active cutting gage sections, either through rollers or through active tungsten carbide cutting structures at the full hole gage sections. Prior art reamers have always been symmetrical in their construction with evenly spaced rollers or reaming blades. A known problem with symmetrical tools is that they can develop a lobe patterned lateral movement cycle that can damage the tools and the condition of the borehole wall. A further problem with prior art string reamers is that they have not had the benefit of force balancing techniques that help to control unwanted lateral oscillations from developing during the course of interaction between the tool and a constricted wellbore. U.S. Pat. No. 5,010,789 (the “'789 Patent”), issued to Brett et al. on Apr. 30, 1991, discloses a method of making imbalanced compensated drill bits. The teachings disclosed in the '789 Patent are incorporated by reference herein.
Additionally, some tools have been recently developed to address the problem of cuttings settling in high angle or lateral hole sections. These tools seek to stir up the cuttings bed by using paddles or chevron-shaped upsets on a sub, or on a piece of drill pipe. However, these cutting bed tools are incapable of addressing the problems of swelling formations.
In view of the foregoing discussion, need is apparent in the art for a tool that can effectively cut swelling formation while doing minimal damage to competent and full diameter borehole walls. Additionally, there is also a need for a tool that can effectively plow out cuttings beds while doing minimal damage to competent and full diameter borehole walls. Furthermore, there also is a need for a tool that can effectively cut free sloughing formations while doing minimal damage to competent and full diameter borehole walls. A technology addressing one or more such needs, or some other related shortcoming in the field, would benefit downhole drilling, for example creating boreholes more effectively and more profitably. This technology is included within the current invention.